This lesson helps introduce students to the concept that temperature causes molecules and atoms to move faster and farther apart, which in turn causes the change from solid to liquid, and liquid to gas.

Smelling Diseases

We all use our noses to make quick judgments from time to time—whether it's checking to see if the milk's still good, or if a shirt needs to go in the wash. This Science Update discusses how doctors are developing a kind of sniff test to screen for diseases.

Transcript

A nose for diagnosis. I'm Bob Hirshon and this is Science Update.

If humans were like bloodhounds, doctors could start your checkup by sniffing you for signs of disease. And someday, with help from a device called the Cyranose, they just might.

Bill Hanson is an anaesthesiologist and critical care expert at the University of Pennsylvania School of Medicine. He says many illnesses make you exhale a distinct chemical signature, which is created by the germs or malfunctions that cause the disease, and your body's efforts to fight them.

Hanson: So the Cyranose is a small device about the size of a pocket radio that sucks gas into it, across its sensors, and then analyzes the response of those sensors and puts that information into a software package.

In early trials, the Cyranose has diagnosed cases of pneumonia and sinusitis—not perfectly, but reliably enough to serve as a screening test.

Hanson: As these tools become more sensitive over time, and more technologically advanced, there's a very good chance that one could walk into a physician's office, and exhale into a device like this, and have a diagnostic screen done for any of a number of different things.

He says the nose could help doctors avoid giving the wrong treatment, and start the right treatment more quickly. I'm Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

You might have thought strange breath odors just came from eating garlic, or not brushing your teeth. But many diseases have distinctive breath signatures. People with liver disease often have a fishy, livery smell on their breath. Kidney disease can cause your breath to smell like urine. Diabetes can produce a fruity, sweet smell. Some of these smells are so strong that they have been used as diagnostic tools since ancient times.

But many other things that go wrong in the body can create odors that aren't so obvious to our insensitive noses. Odors are just gases, after all, and as long as you have a device that can reliably tell one gas from the other, you can spot the marker for that disease.

That's what the Cyranose is for. The immediate goal is to diagnose pneumonia and sinusitis quickly in intensive care words. Patients who develop these conditions need antibiotics as soon as possible. However, doctors are careful not to over-prescribe antibiotics, because doing so helps breed drug-resistant bacteria.

Right now, diagnosing pneumonia accurately involves a battery of blood tests, X rays, and other techniques that take considerable time. But Dr. Hanson's team has found that the Cyranose can spot pneumonia cases pretty accurately just by sampling the gas that the patient exhales.

The goal here isn't for the Cyranose to replace more elaborate diagnostic tools. Rather, it's meant to be a quick screening device that tells doctors whether or not they should continue testing for pneumonia and start treatment just in case. For doctors in an intensive care ward, this could free up a lot of time and energy for other patients, and would also cut down on unnecessary antibiotic use while getting treatment faster to patients who need it.

The researchers plan to refine the device in three ways. First, they'll test it against even more accurate diagnostic tools, to get a clear sense of exactly how reliable the Cyranose is. Second, they'll work with engineers to improve the sensitivity of the device. And finally, they'll keep working on the mathematical models that interpret all the gases in a patient's breath and use them to spit out a "yes" or "no" diagnosis. And eventually, they plan to branch out into other diseases, with the goal of making a single device that could be used to scan for a wide range of medical problems.

Now try and answer these questions:

What is an electronic nose?

How does the nose test for pneumonia?

How are the scientists measuring the nose's accuracy?

Can you think of other uses for an electronic nose besides medical diagnosis?